The present invention relates generally to data transfer between components of radiotelephone equipment and more particularly to a serial digital data transmission system layered on a slower synchronous self-clocking digital data transmission system with message queuing, bus control, and segmented memory transfer features that enable cellular radiotelephone subscriber equipment to respond to requests initiated by cellular system fixed equipment that require a fast response.
A synchronous self-clocking digital data transmission system has been described in U.S. Pat. No. 4,369,516. A synchronous/asynchronous data bus system has been described in U.S. patent application Ser. No. 303,214 "Multiplexed Synchronous/Asynchronous Data Bus" filed on Jan. 27, 1989 in behalf of Wilson, et al, now U.S. Pat. No. 4,972,432.
Patent application Ser. No. 303,214 describes an asynchronous data transmission system layered on a slower self-clocking synchronous data transmission system. The asynchronous data transmission system has much faster data transfer capability than the synchronous data transmission system. This is a particularly useful system in applications where the functions of a portable radiotelephone are integrated with a mobile type radiotelephone peripheral. The portable radiotelephone may then take advantage of the superior mobile type characteristics, such as power output, while using a minimal amount of time for the required transfer of data. (An example of a mobile type radiotelephone peripheral is described in U.S. Pat. No. 4,680,787 "Portable Radiotelephone Vehicular Converter and Remote Handset", hereinafter referred to as a "CVC". This portable/mobile integration is accomplished by splitting radiotelephone functions between the CVC peripheral and the portable radiotelephone.
While the asynchronous data transmission offers higher rates of data transfer, it is desirable to retain the synchronous data transmission system because the synchronous data transmission system has inherently better electrical immunity to transmission error in areas of high electrical noise, such as an automobile environment, and produces little electromagnetic interference itself. Moreover, it is desirable that the synchronous digital transmission system continue in use unmodified to avoid retrofitting equipment already in service.
The invention described in the aforementioned U.S. patent application Ser. No. 303,214 solves some of the problems associated with both high rates of data transmission and required noise immunity. Two uses to which this asynchronous/synchronous data bus may be applied are found in U.S. patent application Ser. No. 107,227 "Radio Arrangement Having Two Radios Sharing Circuitry" filed on Oct.9, 1987, now U.S. Pat. No. 5,029,233 in behalf of Metroka and the aforementioned U.S. Pat. No. 4,680,787. There, the common data bus integrates a portable radiotelephone with a CVC peripheral to give the portable radiotelephone user the radiotelephone performance expected in the higher powered CVC mobile.
For radiotelephone systems being planned for the future, it has been found that an even faster data bus than the one described in the U.S. patent application Ser. No. 303,214 is necessary because subscriber radiotelephone units compliant with cellular system regulator requirements must respond to system queries within a much smaller amount of time than is possible using the multiplexed synchronous/asynchronous data bus of U.S. patent application Ser. No. 303,214. One example of such required responses is a response to cellular system challenges by subscriber equipment which some countries specify. These system queries require the subscriber equipment to process large amounts of data and return the proper response to the fixed equipment within a specified amount of time. A unique implementation to meet this type of requirement in a subscriber unit, where the unit is a single portable or mobile radiotelephone, is found in U.S. Pat. application Ser. No. 461,570, "Radiotelephone Controller Configured for Coresident Secure and Nonsecure Modes" filed on Jan. 5, 1990 in behalf of Pini, et al. In this Application, a method is described whereby the portable radiotelephone's display processor may be used to process the cellular system query thereby avoiding adding hardware to the portable radiotelephone. This is especially important in portable radiotelephone applications where space constraints are rigorous.
However, when a CVC or some other peripheral is to be integrated with a portable radiotelephone on a common data bus as described in U.S. patent application Ser. No. 303214, that data bus cannot guarantee an adequate response to the cellular system queries due to delays caused by inherent data bus characteristics such as the amount of data transfer required to integrate radiotelephone functions over the data bus, the control of the data bus by the contending data transmission systems, and the method of queuing messages into the data bus.
Therefore, it would be desirable to provide a fast data bus that avoids these problems so that subscriber equipment that integrates a portable with a CVC or some other peripheral, is able to respond to these cellular system queries. It would also be desirable to use the microprocessors in the portable radiotelephone to process the system queries in manner similar to that described in the aforementioned U.S. patent application Ser. No. 461,570 because in many applications, particularly portable radiotelephones, the number of bus lines and corresponding connectors and compatibility with existing systems are important considerations. It would also be desirable to retain the same number of signal lines in a combined faster asynchronous/synchronous data bus structure, as well as to retain hardware compatibility with mobile and portable units presently in use.